"My first two thoughts are the MAF sensor and/or the O2 sensor. I would take some MAF cleaner to it and also take out and clean off the O2 sensors using the same MAF cleaner.
'They' say that you can't or aren't supposed to clean the O2 sensors, but I never have had any trouble. They gum up much like spark plugs and everyone knows that you can clean them off. I have been reluctant to use carb cleaner on the O2 sensors, but the MAF cleaner seems to work just fine. I have cleaned mine out twice since I have owned the truck (7 years) and there never seems to be a problem. I will probably do it again soon, too.
Hope this helps. Whenever stuff like this happens with an EFI it always seems to be electrical related and usually something that sends a signal to the ECU is the culprit."
I have also used electrical parts cleaner and been ok!